Vol. 69.] 



THE GENUS AVLOPHYLLUM. 



73 



Fig. 8. — Coral exhibiting 

 effects of rejuvenescence. 

 (Natural size.) 



1 Verjiingungsprocess' from the German of Constantin Milashevich. 1 

 Milashevich, in his discussion of the Aporose coral Montlivaultia 

 describes (loc. cit.) the process as follows : — 



' . . . . unter gewissen, noch nieht bekaanten Bedinguugen der Polypen- 

 stock fast, plotzlich sich einschniiren, und hierauf mehr oder weniger rasch 

 sich wieder ausbreiten und sein Dasein in einer neuen Form fortsetzen kann.' 



Tomes distinguishes rejuvenescence from calicular budding, since 

 the latter gives birth to a number of young corallites, while the 

 former merely produces a reduction in size (and to some extent, I 

 may add, simplification of structure). 



According to PL M. Bernard's 2 theory, rejuvenescence is the result 

 of strobilation, or transverse fission, following which the upper 

 individual would kill the lower one by its weight and lay down its 

 skeleton on the old calyx. The character of rejuvenescence iu 

 Aulophyllum suggests the building of a newer upon an older 

 structure, and in this respect lends support to Bernard's theory. 



Dr. N. Yakovlev, 3 in a still more recent paper, makes the suggestion 

 that the process was called into play to obviate the necessity of 

 further expansion of the calyx. Against 

 Yakovlev's supposition that rejuvenes- 

 cence is an alternative to calicular 

 enlargement, it may be stated that re- 

 juvenescence as demonstrated by Aulo- 

 phyllum may take place in young and in 

 dwarfed individuals. 



The following are the various struc- 

 tural changes observed in Aulophyl- 

 lum : — 



I. The reduction in the diameter of the 

 central column. Attenuation com- 

 mences a little below the point at 

 which the sudden reduction in the 

 diameter of the corallum takes place 

 (PI. IX, fig. 2). 



II. The reduction in number of the septal 

 lamellffi and the crowding of these 

 within the smaller area resulting 

 from the structural change just men- 

 tioned in I (compare PI. IX, fig. 1 c, 

 with figs. 1 a & 1 b). 



III. The straightening out of the mui'al 

 pericentral vesicles into an almost 

 horizontal position, so that they be- 

 come identical in character with the 

 tabular vesicles (PI. IX, fig. 2). 



IV. A gradual reduction of the width 

 of the zone of tabular vesicles, 



[The 



specimen from which 

 j;s. la, 16, & 1 c in 

 PI. IX, and text-fig. 9 

 (p. 74) were cut. 1 a, 1 b, & 

 1 c were cut at a. ..a, b...b, 

 and c.c respectively.] 



Pakeontographica, vol. xxi 



1 'Die Korallen der Nattheimer Scbichten : 

 (1876) pp. 194-95. 



2 Brit. Mus. Catalogue of Madreporarian Corals, vol. vi (1906) pp. 22-23. 



3 ' Die Entstehung der characteristischen Eigentiimlicbkeiten der Korallen 

 Eugosa' Mem. Com. Greol. Bussie, n. s. No. 66 (1910) p. 16. 



